Silicone compositions which are curable by reaction of .tbd.SiH groups with silicon-bonded olefinic groups in the presence of a hydrosilation catalyst are well known in the art, for example, as described in U.S. Pat. Nos. 2,823,218; 3,249,581 and 3,436,366, all of which are incorporated by reference into the present disclosure. Because curing begins upon mixing of the aforesaid ingredients, it is the usual practice to provide addition curable compositions in two packages, one of which contains the olefinically unsaturated polysiloxane and the hydrosilation catalyst, and the other the organohydrogenpolysiloxane crosslinking agent.
When it is necessary to extend the pot life of addition curable organopolysiloxane compositions or provide one-component addition curable organopolysiloxane composition, a cure inhibitor can be included therein. Generally, cure inhibitors are compounds which slow curing at ambient temperatures but do not retard curing at elevated temperatures. Such cure inhibitors are heat deactivated cure inhibitors, or are sufficiently volatile to be expelled from coating compositions at elevated temperature.
Particular heat deactivated cure inhibitors are the dialkylacetylenedicarboxylates. These inhibitors are disclosed in U.S. Pat. No. 4,347,346, to the instant inventor, and are described by the formula, ROOCC.tbd.CCOOR, where R is a monovalent hydrocarbon radical.
It is an object of the present invention to provide platinum catalyzed, addition cured silicone coating compositions containing dialkylacetylenedicarboxylate inhibitors which are curable with ultraviolet light.
It is a further object of the present invention to provide a method to cure platinum catalyzed, addition curable silicone coating compositions containing dialkylacetylenedicarboxylate inhibitors which contains the step of exposing the coating composition to ultraviolet light.